Vitamin D and incidence of diabetes: a prospective cohort study

Summary Background & aims To investigate the relationship between levels of 25-hydroxyvitamin D and the incidence of type 2 diabetes in a Spanish population. Methods We undertook a population-based prospective study in a population from southern Spain. The first phase of the study (1996–1998) included 1226 individuals. Of this original cohort, 988 persons were reassessed in 2002–2004 and 961 in 2005–2007. Measurements were made of 25-hydroxyvitamin D and intact parathyroid hormone in 2002–2004 and an oral glucose tolerance test was done in three time points. Results The incidence of diabetes in subjects with 25-hydroxyvitamin D levels ≤18.5 ng/mL (percentile 25) was 12.4% vs 4.7% in subjects with levels >18.5 ng/mL. The likelihood of having diabetes during the four years of follow-up was significantly lower in the subjects with higher levels of 25-hydroxyvitamin D [OR = 0.17 (0.05–0.61)]. None of the subjects with levels higher than 30 ng/mL developed diabetes. Conclusion In this prospective study, we found a significant inverse association between serum 25-hydroxyvitamin D levels and the risk for type 2 diabetes in a population from the south of Spain.